Research is proposed to establish profiles of the genesis of arteriosclerosis in selected species of captive mammals and birds that have been on controlled diets for significant periods of time. The omnivore diet introduced to the Philadelphia Zoo in 1935 contains 11.5 percent fat with the majority of the lipid present as the unsaturated moiety. Since many of these zoo animals, especially the anthropoid apes (i.e. orangutans - 56 years old, a gorilla - 43 years old) are elderly and have been maintained on these diets for nearly their entire lifespans, histological studies of the arterial systems of the heart, the brain and other vital organs should make it possible to determine the value of long term dietary manipulations to prevent or minimize mortality from arteriosclerosis. Captive woodchucks maintained on this diet for lifespans up to 8 years develop arteriosclerosis of the smaller deep arteries of the heart and brain but the aorta is spared. Cerebral hemorrhages and myocardial infarctions attributed to arteriosclerosis of small and medium sized arteries have occurred, however. Prescribed amounts of cholesterol or saturated fats added to the regular rations of woodchucks beginning at 5 months and 5 years of age and continuing for 2 and 4 year periods will provide comparative data to ascertain whether lipogenic stimuli increase mortality from heart disease and stroke, whether arteriosclerotic lesions regress when lipogenic stimuli decrease, and whether susceptibility of the arterial wall to lipogenic stimuli is a function of age.